Charger Reccommendation Please?

I'm building my first battery pack -

7S13P Samsung 35E with a Daly Electronics 7s 24v BMS http://www.dalyelec.com/product_view_250_109.html

60a 24V common port version https://www.aliexpress.com/store/product/Waterproof-7S-15A-25A-35A-45A-60A-24V-Lithium-Battery-Protection-Board-BMS-Electric-Charge-Li/4165007_32879269241.html?spm=2114.12010612.8148356.2.3e4f6d368IFoG6

once built, I want to manage the battery as carefully as I can to ensure lifespan. I'd appreciate any recommendations for 24v chargers with the appropriate amount of 'intelligence' to complement the BMS I've chosen.

Thank you

Well, you don't need a balancing charger to fill that pack, but since its 7s, you do have the possibility of using RC chargers. Many of them do 1-8 s, and can be set to fill, or discharge, or undercharge. You'd use the non balancing charge settings to charge a bms equipped pack.

Just a thought, that with an RC charger you get some options not usually there in a regular 7s charger. And also, lots of "24v" chargers are 6s.

The #1 requirement for me is user-custom adjustable setpoints.

Besides a quality hobby charger like iCharger, Grin Satiator.

Sterling Pro Charge Ultra series is excellent, but Absorb / CV Hold time is minimum 1hr, so you'd want to lower the voltage setpoint accordingly.

Victron chargers with VE.Bus System Configurator interface.

Mastervolt chargers can also be programmed appropriately using their PC-Link and Master Adjust software.

But really, any PSU where you can adjust volts and amps, once you've got a normal routine, a basic timer cutoff is fine, otherwise manually regulate.

For precise automation, easiest to implement is no Absorb / CV at all, just charge to your setpoint and stop.

The ability to precisely load test is very valuable, for your longevity goal the target should be, end up at true 90% SoC in normal use.

Thanks for the great input - I just realised, since I am buying a diy spot welder that is powered from a 12v car battery, instead of buying another car battery charger £90+ , maybe I can buy one good charger that's suitable for both purposes, recharging the 12v lead acid car battery, and also maintaining this pack.

I think I'd look at the Sterling 24V PCU unit then, coupled with his Battery Chemistry Module, can take care of both concurrently.

Or the Satiator, but that's only one at a time.

john61ct said:

Or the Satiator, but that's only one at a time.

Click to expand...

I looked at the satiator, but that didn't appear to do 12v, rather 24 volt and above. I don't need concurrent use for sure.

Thanks again

Something like this would give tremendous value

https://www.ebay.com/itm/Working-SORENSEN-DCS-40-25-POWER-SUPPLY-0-40-VOLTS-0-25-AMPS-DCS-25M9A/264352509364

go for thousands new, even refurb can be over a grand

I'm unsure how many amps I need. given that I want to preserve the life of the cells - in a 7s13p pack, would I charge at 7x times the amps needed to charge a single cell, or 13x the amps needed to charge a single cell? My brain tells me it's the parallel that increases the amps, but I want to be sure!

The spec on the individual cells says:

3.5 Charging Current Standard charge: 1,700mA
For cycle life : 1,020mA
3.6 Charging Time Standard charge: 4hours
3.7 Max. Charge Current 2,000mA (not for cycle life)


BMS Specs say
Charge Charge voltage 29.4 V
Charge current 60A
Over charge protection Over charge detect voltage 4.25±0.025 V
Over charge protection delay 0.5 S
Over charge release voltage 4.19±0.05 V
Balance Balance detection voltage 4.18 V
Balance release voltage 4.18 V
Balance current 35 mA Balance current35±5mA

so if I understand it correctly, charge each cell at 1 amp to preserve cycle life. 13A seems like a pretty high load charger though..

If I can find a good 10A 29.4v charger, would that be an appropriate amount of amps?


thanks

Best is a normally low charge rate, .1-2C, .3C as a stressful maximum. Occasional faster charging only when needed, hits lifetime cycles assuming otherwise well treated.

CC only only "charge to" a termination voltage, say 4.05V or whatever gets you to 90% SoC or less compared to maker max spec voltage.

And yes parallel determines capacity, serial only affects voltage, so judge C-rate off 13x the actual capacity, not maker rating.

Your actual charger should be rated at least 20% higher than the max current you'll ever use, but let you scale amps up or down as needed.

Its PSU (if DCDC setup) should be rated 20% higher than the maximum your charger can pull in theory.

Thanks for the advice so far, It's helped a lot.

I liked the cycle satiator a lot, but being in the UK, the 24v version would cost around £350 after import duty, customs handling fees etc.

ISDT T8 at £85 seems a good dc-dc charger.
https://www.isdt.co/t8.html?lang=en

I found a fantastic deal on a meanwell 750W ac-dc psu which I think will be perfect to match it,even if it doesnt exceed the max 1000W the charger is theoretically capable of sucking (I'm not buying a 1200W PSU needlessly - my current use case only needs 400W )

https://www.meanwell.com/webapp/product/search.aspx?prod=SP-750

Looks like it can spit out 27.8Amps at 30V - my pack will be charged at 13.26A at 29.4V so the psu should have plenty of overhead for any future projects,

It's not from their cheapo range either, it's got power factor correction and retails at around £200 , this guy on ebay seems to have 10 of them used and is looking for £70

https://www.ebay.co.uk/itm/192900555027

So I reckon that's a sweet enough charging setup for £135 total

13P is going to (try to) pull how many Amps when depleted?

Pretty sure if you don't go for a proper charger you'll need at least a constant current limiting PSU.

That psu is just to feed the isdt t8 dc to dc "proper" charger

great

Just need to build a decent enclosure for it now