12v battery charging question (lead-acid vs. lithium)
 

So I have a question.

It seems that it is either time now or time soon to replace Black & Green's deep cycle battery.

This is the current battery (five years old):
https://www.batterymart.com/p-odysse...SABEgLSL_D_BwE

I have a 25 amp "three step charger" also from Odyssey:
ODYSSEY battery - Ultimizer

My question is whether I can use that charger to charge this battery:
https://www.lithiumion-batteries.com...m-ion-battery/

That lithium battery is nearly twice as expensive as a new Odyssey battery, but it is rated for 5 times as many charge cycles. And it is 30 pounds lighter.

Any reason that I shouldn't use my existing charger to charge it?

Consider the amperage of the Honda's alternator output is two or three times greater than the 25 amp charger.

Need to have a charger with a good gel battery setting that won't try to equalize or go above about 14.6v
Looks like you absolutely do not want to use that Odyssey charger on a lithium.

My only dislike of lithium batteries is centered around their cold weather performance.

Remember I have built 3 different lithium batteries for 2 vehicles and been using lithium vehicle batteries since 2011.

I don't know that I want to put all that extra money down for another charger, I guess. Thanks. I got five or six years and a few thousand cycles out of the battery. I treated it well. Never depleted it heavily. Charged it generally for 12 or 14 solid hours over night. I have a desulfinating three stage charger. Odyssey is good hardware. Maybe I'll just buy another one of their batteries.

A $50 to $70 digital charger that makes 10 to 15 amp with "standard" or "flooded" setting, an "AGM" and a "gel" setting will be all you need.
You don't have to spend much money to get a special lithium charger.

Charging the lithium will be much more efficient than a lead acid. The lead acid probably requires around 4hr of float time. As soon as the lithium battery hits 14.4 to 14.6 it's all charged up.

You're good to go. It's designed as a drop-in replacement for a lead-acid.

Might want to check what kind of charging amperage your alternator is putting in to it, mind you. The BMS may or may not regulate it down to 35 amps.

It makes sense that they might design the battery so that it could protect itself from alternators that would have been designed for lead acid batteries.

Here is a screenshot from the factory service manual on my civic:
http://ecomodder.com/forum/attachmen...1&d=1513015096

As you can see it seems to run at 75 amps? That's more than I thought.

Also, if I got the 35 amp hour battery wouldn't I need a charger that equals at least half for 60 percent of the amperage rating of the battery? So perhaps maybe a 20 or 25 amp charger?

75 amps peak (which it should be able to hit by typical driving speeds, say 2000rpm). Less at idle, usually. Minus all electrical loads on it while running - at least 10 amps. Turn the lights and the blower on and you're probably looking at more like 30+ amps.

And how much amperage goes in to the battery is all relative to the voltage difference between what the alternator is putting out and what the battery is sitting at. If your alternator is putting out 14.4v and your battery is sitting at 13.8 already, there's only 0.6v difference, and not a lot of current is going to flow in to the battery (even if the internal resistance is in the milliohms). If your battery is sitting at 10v and the alternator is trying to put out 14.4v, there's 4.4v of difference and a lot of current is going to flow.

You could build a circuit that would limit how much current goes in to the battery, should it turn out that the BMS doesn't do this. That's more annoyance and headache, mind you.

Oh, and considering the time of year...you don't want to charge LiFePO4 batteries below freezing...it will mess them up, and you will supposedly lose 20% of capacity. It will only happen once, mind you. That battery is meant as a replacement for wheel chairs or maybe electric bikes...it's probably not designed or going to handle the severe temperature changes in an engine compartment.

Don't worry about your chargers' output, unless it's more than the battery can handle. You could charge it at 1 amp and it will still charge up properly.

You'll have to decide if it's worth the effort to tackle these issues. Better to hear them now then to have a nasty surprise later.

A normal truck sized lead acid battery soaks up about 2 amps to float it from full charge 12.8v resting voltage to 14v.

It's actually 20°F. You don't want to charge LiFePO4 batteries when their below 20°F. Freeze they should be fine.

My LiFePO4 batteries have lasted so long because they are not in the engine compartment.

The $200+ difference would buy a lot of gas and 30lbs isn't going to make a big difference. I would stick to what works or try to source a less expensive lithium pack.

Used Nissan leaf cells are around $350 On fleabay. 4 cells at 3.7v per cell and roughly 80ah. Might take some extra parts but a much larger battery.

I've been planning to relocate the battery to the former spare tire well in the trunk. It doesn't look like these lithium batteries can take the high heat of an engine compartment, from what I'm reading and what you all are saying.

I am in Coastal Southern Cali... It almost never ever freezes here, except high in the mountains. 20*F has quite probably not happened at my garage location in 20,000 years! Lol

The leaf LiFePO4 batteries were heat damaged by AZ summer heat, which isn't any where near underhood level.

I'm running this in my Prius with no balancing.

http://www.batteryspace.com/lifepo4-...assed-dgr.aspx

There are coupon codes for 5% off to basically give you free shipping. Run 2 in parallel if you need more capacity. The code I found is E7SEA

Everything I've read says not to charge below freezing. I replaced the Prius battery with a LiFePO4. The stock battery compartment is inside the cabin, so that helps it to stay warm, or cool depending on the weather. With our 26 degree days, I'm guessing the battery is getting near freezing. No issues in the past 2 years.

20f isn't that far below freezing, IMO.

The data sheet for my LiFePO4 cells shows a charging range of 0°c-30°c, which prompted me do more research. After reading what I could find, I have no intentions of charging below 0°c.

It may just be that they are giving me a 6°c buffer (20°f vs 32°f), but why chance it on something this expensive?

Anyone looking for cold temperature versions, check out LiFeYPO4 cells.

This is exactly the battery to get. For a car, you need the higher C cells because at 1 or 1.5 or even 2C, you'd need a massive battery to prevent the alternator from frying it. That pack at 20Ah can absorb perhaps a 60A charge (3C charge rate, pretty normal for cells optimized for power) without hurting it too badly. On older cars with 80-90A alternators, after subtracting the amps needed for the ECU/fuel pump/relays, you'd be right around there if the engine is revved a little and a bit under at idle. I think it is a good idea to idle for a bit to bring the voltage up if the car has been sitting for a few days to reduce the rate at which the battery charges. Preventing 1 dollar worth of battery damage is worth a lot of gasoline.

On a car that comes with a bigger battery/alternator/starter, I would probably put two of those together for 40Ah.

Supposedly some LiFePO4 cells can take charging at maybe 25F but not much below that, if you have cold winters I think it is smarter to run lead acid. I would certainly skip the lithium if it snows where I live.

I wouldn't get larger/multiple batteries just to provide enough cranking amps to the starter, or to absorb large alternator currents. The solution to either too much cranking draw from the battery, or too much charging from the alternator would be to run supercaps in parallel to the battery, and placing a high watt, low ohm resistor between the battery and supercap. This would limit draw/charge on the battery, and offload big spikes to the supercap. It would also allow the battery to be moved inside the vehicle using relatively thin gauge wire. Moving the battery inside the cabin would help regulate temperature, and make it more convenient to disconnect and put on a charger if you wanted to run an alternator kill switch.

Here's a poorly done video I made explaining the battery/resistor/supercap concept.

https://www.youtube.com/watch?v=LX_o3hl2Dv4

That's cool, redpoint. I have been wondering about capacitors ever since someone posted their "boost pack" capacitor thread here. I have no experience with capacitors. But a question... a main purpose for my battery set up in charging the battery from the grid, using the deep cycle capacity for all electrical needs as I drive the car, and occasionally doing some regen braking by turning the alternator on while in deceleration fuel cut-off mode. The capacitors would probably be better than a battery for regen because they will absorb more energy from the 75 amp alt more quickly than the battery can. But the grid charging? The capacitors would be problematic maybe? Could I continue to run separate charging lines straight to the battery from my on board grid charger and recharge the battery without problems?

The problem is not the cranking amps, that 20Ah should have no trouble cranking most engines.

The problem is that parasitic draw while the car is sitting lowers the battery voltage, and causes increased charging current when the car is started. This is bad for the battery's life.

Ultracapacitors make the problem worse because they have leakage. I believe they are best paired with an undersized cheap lead acid since those are the batteries that tend to have trouble providing enough power to crank an engine.

I wish I could install lithiums. Sometimes we have a day where it hit's -40... both C and F. This morning it's 8f/-13c, and it's going to be a lot colder in January and February.

Any ideas? Simply relocating it to the hatch isn't going to be enough if the car sits in the cold for 16 hours.

And, FWIW, I'd probably use these:

https://www.ev-power.eu/LiFePO4-smal...e-CE.html#tab2

4 cells = 12.8v nominal, 14.6v peak, same as the cheaper battery you were looking at. 8 cells would = the more expensive one. You'd need to put bars between them but it's also easy to take the cells apart and re purpose them.