- Messages
- 13,439
- Reaction score
- 10,030
- Location
- Port Orchard, Washington State
- # of dives
- 1000 - 2499
I'd be (very) surprised if the BMS let's you get to 75.6V without changing the 4.13V per cell setting in the app to 4.2V.
Battery charger for Genesis and other DPVs
- Thread starter stuartv
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
OP
Jon Nellis
Contributor
I'm now getting emails referencing this thread with individuals thinking some of the ideas expressed here are "good ideas". Let me clarify, they are not.
I'm fairly certain most divers would reject an 80% gas fill from their local dive shop and want it topped off. Most divers would also agree that intentionally planning a dive with an 80% breathing gas fill is not a good practice, when it hurts nothing to fill a tank to 100%. Sure, if you have ample gas and are not planning a long dive, you can probably get away diving with a short fill once in a while, since topping it off is not as simple as plugging a cord into an outlet.
Now translate that to a DPV battery. It does not hurt the Warp Core battery to charge it to 100% before a dive. Not sure where anyone got the idea 100% charges are detrimental before diving the Genesis, but they are not, since the Warp Core already ends the charge early 4.12V/cell. The idea of ending a charge at some random premature value like 80% will significantly increase DPV battery life is missing a serious bit of context. That bit of context is that the cells only have a typical 7-8 year service life before the internal chemistry starts failing due to oxide and plating build up. Since most divers don't do 60+ full cycles a year, every year, for 8 years, they are not getting close to full utilization of the battery before it will need the cells replaced due to age, regardless if you charge to 80% or 100%.
Things that decrease a Lithium battery's life are...
1. High temperatures. Don't leave that black DPV (aka: solar oven) sitting in the sun.
2. High power draw in the last 15-20% of charge is detrimental and generates a disproportionate amount of heat. (why we implement a power reduction near end of charge)
3. Long term storage above 4.1V /cell (exacerbated by high temps)
You do want to avoid using the last 20% of the battery to prolong it's life, but placing an additional (unnecessary) limit of an 80% charge really reduces your planned capacity to 60%. Since it's highly unlikely most people will ever get close to using the full potential of a lithium DPV battery before it times out from age, it's a horrible idea to unnecessarily restrict charging, when it provides no significant benefit, but could leave you sh1t out of luck if a current kicks up or you need to tow a buddy home using more power than anticipated. There's no significant upside to a 80% charge, only downside.
Sure, if you have a Warp Core with a 1300-1700Wh battery and are only planning to do one or two dives simple dives, then you might be fine with a short charge, just like doing an average dive on a short filled 130cuft tank.
If you are worried about charging to 100% and then cancelling the dives, just leave the motor running in air at full speed for a couple hours to drain the battery a bit. Makes a decent fan.
Value wise, let's look at cost. The 3.1 is around $350 for a set of cells. Over 8 years, that's $44 per year or let's estimate it at $1 a charge or around 50 cents per dive, since most people have no problem getting at least 2 long dives per charge with ample reserve power. Now I'll be VERY OPTIMISTIC AND GENEROUS and say you get an extra 2 years with an 80% charge routine. It's now 80 cents per charge or 40 cents per dive from the same set of cells. Is saving, AT MOST, 10 cents a dive worth the risk of running out of battery and having to surface swim back, risking getting hit by a boat (since you'll probably also run out of back gas while swimming with a dead DPV, before getting to your exit point)??? I'm pretty sure you wasted way more than 10 cents worth of un-drunk coffee that got cold this morning, is your added safety of a full charge not worth a dime???
Cheers,
Jon
I'm fairly certain most divers would reject an 80% gas fill from their local dive shop and want it topped off. Most divers would also agree that intentionally planning a dive with an 80% breathing gas fill is not a good practice, when it hurts nothing to fill a tank to 100%. Sure, if you have ample gas and are not planning a long dive, you can probably get away diving with a short fill once in a while, since topping it off is not as simple as plugging a cord into an outlet.
Now translate that to a DPV battery. It does not hurt the Warp Core battery to charge it to 100% before a dive. Not sure where anyone got the idea 100% charges are detrimental before diving the Genesis, but they are not, since the Warp Core already ends the charge early 4.12V/cell. The idea of ending a charge at some random premature value like 80% will significantly increase DPV battery life is missing a serious bit of context. That bit of context is that the cells only have a typical 7-8 year service life before the internal chemistry starts failing due to oxide and plating build up. Since most divers don't do 60+ full cycles a year, every year, for 8 years, they are not getting close to full utilization of the battery before it will need the cells replaced due to age, regardless if you charge to 80% or 100%.
Things that decrease a Lithium battery's life are...
1. High temperatures. Don't leave that black DPV (aka: solar oven) sitting in the sun.
2. High power draw in the last 15-20% of charge is detrimental and generates a disproportionate amount of heat. (why we implement a power reduction near end of charge)
3. Long term storage above 4.1V /cell (exacerbated by high temps)
You do want to avoid using the last 20% of the battery to prolong it's life, but placing an additional (unnecessary) limit of an 80% charge really reduces your planned capacity to 60%. Since it's highly unlikely most people will ever get close to using the full potential of a lithium DPV battery before it times out from age, it's a horrible idea to unnecessarily restrict charging, when it provides no significant benefit, but could leave you sh1t out of luck if a current kicks up or you need to tow a buddy home using more power than anticipated. There's no significant upside to a 80% charge, only downside.
Sure, if you have a Warp Core with a 1300-1700Wh battery and are only planning to do one or two dives simple dives, then you might be fine with a short charge, just like doing an average dive on a short filled 130cuft tank.
If you are worried about charging to 100% and then cancelling the dives, just leave the motor running in air at full speed for a couple hours to drain the battery a bit. Makes a decent fan.
Value wise, let's look at cost. The 3.1 is around $350 for a set of cells. Over 8 years, that's $44 per year or let's estimate it at $1 a charge or around 50 cents per dive, since most people have no problem getting at least 2 long dives per charge with ample reserve power. Now I'll be VERY OPTIMISTIC AND GENEROUS and say you get an extra 2 years with an 80% charge routine. It's now 80 cents per charge or 40 cents per dive from the same set of cells. Is saving, AT MOST, 10 cents a dive worth the risk of running out of battery and having to surface swim back, risking getting hit by a boat (since you'll probably also run out of back gas while swimming with a dead DPV, before getting to your exit point)??? I'm pretty sure you wasted way more than 10 cents worth of un-drunk coffee that got cold this morning, is your added safety of a full charge not worth a dime???
Cheers,
Jon
Jon Nellis
Contributor
Makes sense. I got a nice zap from the 20s pack(not for a dpv) I built a while back, haha.
The added cell wear above 4.1v/cell is disproportionate to the wh you gain from it. Having the charger cut at 4.12 lets the cells settle around 4.1 once they are off the charger.
Solid battery engineering all round.
I currently run my re-batteried 1200 around 4v per cell since I often end up not running it for a week or so and bumping it up to 4.1 just before I leave for a dive is easy.
Solid battery engineering all round.
I currently run my re-batteried 1200 around 4v per cell since I often end up not running it for a week or so and bumping it up to 4.1 just before I leave for a dive is easy.
OP
Totally my fault, but I managed to fry my Genesis with this charger. I posted the full story here:
scubaboard.com
One question that was raised here is why anybody would want to charge the scooter to anything less than "Full". Jon posted a very detailed breakdown of why there is no benefit to charging to, for example, 80%.
I want to throw out my "reasoning" for why I do want that capability.
I don't get to scooter nearly as often as I would like. My scooter is often going to need a top-up charge in between dive trips. Or, it HAS. Maybe it won't need them hardly ever now that it's fixed (see other thread).
If I'm doing a top-up charge while it's stored, I want to charge it to 80%, not 100%. And I don't want to achieve that by connecting the factory charger and then sitting there watching it with the BMS app until it's at 67V or 72V or whatever, then unplug the charger. I want to just connect it to a charger that will charge it to the right voltage and then stop.
Why does this make sense - in my mind? Because Jon himself has posted that if you, for example, charge it to full then don't get to dive, you can (should?) just turn it on max and let it run in air until the battery discharges down to a good storage level. Okay. In that case, I don't want a top-up charge for storage to charge it to 100% just for me to then have to run it for a few hours to discharge it back down to 80%. Using a charger that will stop at the right voltage seems to make good sense, to me.
Or, should I just not worry about charging it to 100% for (continued) storage?
I'm really hoping this is now moot. I was having to top-up the charge at least once a month, to keep it from dropping below 62V. But, that was because it was broken and I didn't know it.
Now, it is entirely possible that I'll come back from trips MOST of the time and it will sit stored, with whatever charge I came home with, and still not drop to 62V before the next time I am going to use it. In which case, I would just charge it to Full.
Fingers crossed on that.
Big kudos to Jon/Logic - I fried my Genesis, a cautionary tale
Short version: I fried my Genesis 2.1 using an aftermarket charger. I shipped the tube and warp core to Jon at Logic. He received it yesterday and it is repaired - for a reasonable price - and on its way back to me today. Long version: I got a Satiator 75V battery charger from Grin...
One question that was raised here is why anybody would want to charge the scooter to anything less than "Full". Jon posted a very detailed breakdown of why there is no benefit to charging to, for example, 80%.
I want to throw out my "reasoning" for why I do want that capability.
I don't get to scooter nearly as often as I would like. My scooter is often going to need a top-up charge in between dive trips. Or, it HAS. Maybe it won't need them hardly ever now that it's fixed (see other thread).
If I'm doing a top-up charge while it's stored, I want to charge it to 80%, not 100%. And I don't want to achieve that by connecting the factory charger and then sitting there watching it with the BMS app until it's at 67V or 72V or whatever, then unplug the charger. I want to just connect it to a charger that will charge it to the right voltage and then stop.
Why does this make sense - in my mind? Because Jon himself has posted that if you, for example, charge it to full then don't get to dive, you can (should?) just turn it on max and let it run in air until the battery discharges down to a good storage level. Okay. In that case, I don't want a top-up charge for storage to charge it to 100% just for me to then have to run it for a few hours to discharge it back down to 80%. Using a charger that will stop at the right voltage seems to make good sense, to me.
Or, should I just not worry about charging it to 100% for (continued) storage?
I'm really hoping this is now moot. I was having to top-up the charge at least once a month, to keep it from dropping below 62V. But, that was because it was broken and I didn't know it.
Now, it is entirely possible that I'll come back from trips MOST of the time and it will sit stored, with whatever charge I came home with, and still not drop to 62V before the next time I am going to use it. In which case, I would just charge it to Full.
Fingers crossed on that.
OP
The following is just one data point, and for a Genesis 2.1. It could be different for different voltage levels, different temperatures, and, of course, for a G3.1. And certainly, for a 2.2/3.2. And, I expect, for other variables as well.
When I first got my Genesis, I was trying to figure out what I should expect for voltage drop when it is stored. I could not find any numbers, at all. Had I been able to get the data I have now, I think I would have been able to know that something was wrong with my scooter before I jumped in the ocean with it and fried a charging pin.
I charged mine early last week to just under 73V (with the factory charger - unplugging it well before it was done and the LED went green).
I have been monitoring the pack voltage using the iPhone Bluetooth BMS app every day.
It has been sitting in my living room (i.e. about 70F degrees), with the charging connector cap removed.
It has been consistently dropping about (very roughly) 0.03V each day.
It has gone from 72.97V to 72.66V in 9 days. That averages to 0.03V per day as well.
If I extrapolate that to 30 days, that suggests that I should expect it to drop about (very roughly) 1.0V per month. At least, when it's in the 72V range and stored in my climate-controlled living room. No idea if the self-discharge rate would be expected to be different if the pack started at, say 65V.
I'm sharing this so that others can potentially tell if they need to investigate further to figure out if they have a problem.
Before the repair Jon just did for me, mine was self-discharging at more like 5V per month or something like that. I didn't record the data as I am doing now. I just noted that over a period of 2 or 3 (? or 4?) months, I was needing to do a top-up charge every time I checked it, which was every probably 3 - 6 weeks.
That seemed "too often", to me, but without numbers like I'm collecting now, I had no way to really know that I should dig deeper.
Now I know that it should be good to sit for 6 months* between charge top-ups, if Fate frowns upon me and I don't get to dive with my Genesis in that amount of time.
* 6 months or more. The manual says "When storing the DPV for more than a few days, the batteries should receive a partial charge to bring the voltage into the storage range of 62V to 67V if the voltage is lower". So, if it is at 72V (for example) and drops 1V per month, it will be 10 months before it gets to 62V. Charging it to bring it to 67V means it should be 5 to 6 months before it drops below 62V and needs to be brought back into the storage range again.
I sure hope mine never sits for more than 5 months at a time!
When I first got my Genesis, I was trying to figure out what I should expect for voltage drop when it is stored. I could not find any numbers, at all. Had I been able to get the data I have now, I think I would have been able to know that something was wrong with my scooter before I jumped in the ocean with it and fried a charging pin.
I charged mine early last week to just under 73V (with the factory charger - unplugging it well before it was done and the LED went green).
I have been monitoring the pack voltage using the iPhone Bluetooth BMS app every day.
It has been sitting in my living room (i.e. about 70F degrees), with the charging connector cap removed.
It has been consistently dropping about (very roughly) 0.03V each day.
It has gone from 72.97V to 72.66V in 9 days. That averages to 0.03V per day as well.
If I extrapolate that to 30 days, that suggests that I should expect it to drop about (very roughly) 1.0V per month. At least, when it's in the 72V range and stored in my climate-controlled living room. No idea if the self-discharge rate would be expected to be different if the pack started at, say 65V.
I'm sharing this so that others can potentially tell if they need to investigate further to figure out if they have a problem.
Before the repair Jon just did for me, mine was self-discharging at more like 5V per month or something like that. I didn't record the data as I am doing now. I just noted that over a period of 2 or 3 (? or 4?) months, I was needing to do a top-up charge every time I checked it, which was every probably 3 - 6 weeks.
That seemed "too often", to me, but without numbers like I'm collecting now, I had no way to really know that I should dig deeper.
Now I know that it should be good to sit for 6 months* between charge top-ups, if Fate frowns upon me and I don't get to dive with my Genesis in that amount of time.
* 6 months or more. The manual says "When storing the DPV for more than a few days, the batteries should receive a partial charge to bring the voltage into the storage range of 62V to 67V if the voltage is lower". So, if it is at 72V (for example) and drops 1V per month, it will be 10 months before it gets to 62V. Charging it to bring it to 67V means it should be 5 to 6 months before it drops below 62V and needs to be brought back into the storage range again.
I sure hope mine never sits for more than 5 months at a time!
Similar threads
