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.