LifePo4 batteries and charging ...

ddanley

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Sep 10, 2021
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34
I have two Ampretime 12V 200AH batteries arriving soon. According to the documentation, it states to fully charge each and hook them up in parallel for 12-24 hours. Once that is done, hook them up in series for a 24V system.

I have a Schumacher 12V charger (SSC 1000A) that has Standard / AGM and GEL battery settings. Can I use this charger? If so, which setting should I set it on?

Thank you in advance!

Attached charger manual Just in case...
https://www.batterychargers.com/sites/default/files/manuals/0099000909-03.pdf

D-
 

FilterGuy

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Nov 26, 2019
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Los Gatos CA
The manual does not say what the charge voltages are so it is hard/impossible to give a definitive answer.

The manual says this
Use this button to set the type of battery to be charged.
• 6V
•12V
•Regular (Standard)
•AGM
•GEL
  • My guess is the 6V and 12V settings just charge to 6V and 12V respectively.... this would be too low for LiFePO
  • My guess is that 'regular' is for flooded lead-acid. FLA generally charges to ~ 14.8 V this would be too high for LiFePO4. Furthermore, if the charger has an equalization cycle it could damage LiFePO.
  • AGM usually charges to 14.6V - 14.8V. This would be too high for LiFePO
  • GEL usually charges to ~14.4V and has no equalization. This would work OK for LiFePO4
So, without further data, I would say the GEL setting would be best. However, without better specs, nothing can be said definitively.
 

Substrate

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Poor choice. Avoid the Schumacher speed chargers. What you will notice when you charge lead-acid, is about a 0.6v difference between what is on the display, and what is actually measured at the battery *terminals*.

I know, because years ago, I took the time to do so and purposely trashed NEW agm's just to prove it. So the tip for any agm'ers out there is that with these speed chargers - use the gel setting instead! Sets you up for total confusion trying to explain this to others who assume that all other chargers should be treated like this.

Hence, the so-called gel setting is actually ok for most AGM's, that can handle a 14.6v terminal voltage.

To add insult to injury, part of their algorithm is to do a 15 volt zinger at the end of absorb before dropping to float. It doesn't last long, but can be seen one actually tracks what they do on measuring equipment.

Your bms won't like that, and hopefully would cut off that 15v zinger at the end of charge.
 

ddanley

New Member
Joined
Sep 10, 2021
Messages
34
Poor choice. Avoid the Schumacher speed chargers. What you will notice when you charge lead-acid, is about a 0.6v difference between what is on the display, and what is actually measured at the battery *terminals*.

I know, because years ago, I took the time to do so and purposely trashed NEW agm's just to prove it. So the tip for any agm'ers out there is that with these speed chargers - use the gel setting instead! Sets you up for total confusion trying to explain this to others who assume that all other chargers should be treated like this.

Hence, the so-called gel setting is actually ok for most AGM's, that can handle a 14.6v terminal voltage.

To add insult to injury, part of their algorithm is to do a 15 volt zinger at the end of absorb before dropping to float. It doesn't last long, but can be seen one actually tracks what they do on measuring equipment.

Your bms won't like that, and hopefully would cut off that 15v zinger at the end of charge.

I did a test yesterday with the charger on a lead acid battery. I stopped the test when I saw 14.9 volts and it was still climbing (On the volt meter). I decided then that I wasn't going to use it.

The plan now is to get the batteries as close as possible by drawing down the one that has more power. Then connect them in parallel for 24 hours.

I will then use the growwatt inverter to charge up the batteries. Do this plan sound acceptable, of should I invest in a new charger?

Thanks!
 

RCinFLA

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Jun 21, 2020
Messages
1,028
I would be careful using a 'smart' charger like some Schumacher for LFP battery. Some models trigger an over 15v lead-acid type equalization cycle based on rate of charging voltage rise between 13.5v and 14.5v.

If you use it I suggest you manually disconnect it when it gets to 13.6v or sit there and watch it until it gets to 14.4v then disconnect it. Don't leave it unattended above 13.6v.

If charger has a gel cell or AGM setting you might try that.
 
Last edited:

Substrate

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I did a test yesterday with the charger on a lead acid battery. I stopped the test when I saw 14.9 volts and it was still climbing (On the volt meter). I decided then that I wasn't going to use it.

Yes - you see it !! That is why I totally cringe anytime someone uses a Schumacher speed-charger due to the large 0.6v disparity in voltage as actually seen at the battery terminals!

They are designed primarily to get some old knackered automotive batteries that are highly sulfated working enough to get you to work or at least to the store to get a new battery. But for normal maintenance? Not for me.

So, the 0.6v higher than normal voltage means that they are not suited for gels. And actually usable for agm, but only if you *trick* it by using the lower voltage gel setting. On any other charger, using gel settings for agm batteries results in an undercharge, but on these speedchargers, that is the trick.

If you use the agm setting, you can easily get up to 15.1v in the absorb cycle, which most agm's start going rice-crispy. So yeah, in a pinch for me, they are only suitable for normal charging of agm's using the gel-setting trick.

Perhaps try doing the same by using the gel setting if you must. I never tested the speedchargers long enough to see if they also do the 15v kicker at the end of absorb like they did in the agm setting.

Personally if you are looking for a multi-purpose vehicular agm/flooded/LFP charger, the newer black-cased NOCO's that have an LFP setting and do it right by not doing any float when you set it for LFP, would fit the bill.
 
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