Ryobi Zero-Turn Mower SLA to LiFePo4 Conversion - (Updated - Build Complete With Pics!)

[UltrasoundJelly]

you have a week to recharge, and use it in the summer. How about PV panel(s) and an SCC? Set voltage high enough for BMS balancer to work, low enough to not charge battery too high.

My shed is in shade for 90% of the day, so I'm not sure if that's a viable solution.

 

[Hedges]

If 2 hours good sun around noon, might still be. Otherwise, if panels could be mounted remotely.

Small SCC can be modestly priced, and if they have adjustable voltage could avoid over charge. Possibly could be fed from AC source.

AC chargers, would need to be able to set suitable voltage. Possibly a couple diode drops in series could reduce voltage to what you want. Diode may allow charge to continue slowly to higher voltage, would have to evaluate whether that is an issue. Spring-wound timer on AC side would stop the charging. Diode would also prevent battery from powering anything in charger (but might prevent smart charger from recognizing and evaluating battery.)

People get CV/CC bench supplies to top-balance cells. One that goes high enough could charge the 48V battery. But need to be able to lock CV setting against accidental adjustment (digitally programmed would avoid issue of bumping analog knob). Also, if desired profile is to charge to a "boost" voltage then float, bench supply alone wouldn't do that. Timer might take care of it.

 

[UltrasoundJelly]

Has anyone thought about not using the bus bars, instead using large gage wires with crimp ring connectors? I know this is almost blasphemy in this forum, but many here are building batteries to sit in their basement, while we have the extra mechanical stress of hitting bumps and holes in an unsuspended vehicle. I plan to lock down by batteries, but having some mobility between cells may prevent future sadness. Thoughts?

 

[UltrasoundJelly]

Ooh, just found this charger. Check out the data sheet, it's programmable via a serial cable to set Vcharge, Vfloat, and current as needed. It says potentiometer (or via PMBus Protocol on serial connection) for voltage. Current adjustable as well, but it might just only be via PMBus Protocol.

RPB-1600-48 MEAN WELL USA Inc. | Battery Products | DigiKey

Order today, ships today. RPB-1600-48 – Enclosed Battery Charger 57.6V 27.5A 48V from MEAN WELL USA Inc.. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.com

It seems like a Cadillac of customizability. $354 here:

RPB-1600-48 MEAN WELL | Jameco Electronics

MEAN WELL RPB-1600-48 Battery Charger. Products in stock and ready to ship. Quotes, samples and datasheets available at Jameco Electronics.

www.jameco.com

Would be sweet to be able to adjust the output manually with the pot, and would be absolutely necessary for the high default current (27A) using the Ryobi-provided cable. The PMBus protocol via the CN500 connector seems somewhat obscure. I did find this inexpensive PMBus USB adapter, but the pinout doesn't match up in number or function:

https://www.renesas.com/us/en/products/power-power-management/digital-power/digital-integrated-fet-regulators/islusbeval1z-usb-pmbus-adapter-and-cable

 

[bobbie_ohio]

To which set of wires are you referring can’t handle the load and now many amps is the included lead acid charger putting out?

 

[UltrasoundJelly]

To which set of wires are you referring can’t handle the load and now many amps is the included lead acid charger putting out?

The charger port wires are 14 AWG and the current output of the supplied Delta Q charger is 13A.

 

[bobbie_ohio]

The charger port wires are 14 AWG and the current output of the supplied Delta Q charger is 13A.

Thank you, yes I saw that when I actually focused on looking for the answer. I see a 48v 25a charger for lithium out there that has alligator clips. I’d need to run thicker wires with a new connection anyway if I didn’t want to butcher the original charger/cord

 

[rio]

Nice find on that charger! And also nice find on the current adjustability of the AIMS. This makes the AIMS very appealing.

I'm tempted to just stick to the Delta charger for now. It seems to me that the main differences between SLA and LiFEPo chargers have to do mostly with what happens at the upper voltage limit (absorption, float, etc), after the charger switches from CC to CV. But if we only want to charge to 90%, then we should still be in CC mode, which will be the same regardless of the type of charger. I think disconnecting the charger either with a timer or via BMS overvoltage protection (or both for extra piece of mind) should be fine, especially given the low cycles in our application (and the fact that we're charging only at ~0.15C). I'm going to look more into this because I could be way wrong.

More on the topic of not relying on the BMS for cutting off: How would this be any different if I bought a fancy "smart" LiFEPO charger? Such a charger would not know if an individual cell goes out of balance and hits 3.65V well before the other ones. If this is the case (which is not unlikely), then the BMS would have to step in every single time. Even if I can adjust the total charge voltage down, nothing would guarantee that a single cell would not hit 3.65V before the whole pack reaches the charge voltage. Obviously that's what the BMS is for. Therefore, I think of "overvoltage protection" as a needed routine feature, rather than as "uh oh, something went wrong". Again, I'm just thinking out loud here; there is obviously a lot that I don't know about this topic.

 

[UltrasoundJelly]

Nice find on that charger! And also nice find on the current adjustability of the AIMS. This makes the AIMS very appealing.

I'm tempted to just stick to the Delta charger for now. It seems to me that the main differences between SLA and LiFEPo chargers have to do mostly with what happens at the upper voltage limit (absorption, float, etc), after the charger switches from CC to CV. But if we only want to charge to 90%, then we should still be in CC mode, which will be the same regardless of the type of charger. I think disconnecting the charger either with a timer or via BMS overvoltage protection (or both for extra piece of mind) should be fine, especially given the low cycles in our application (and the fact that we're charging only at ~0.15C). I'm going to look more into this because I could be way wrong.

More on the topic of not relying on the BMS for cutting off: How would this be any different if I bought a fancy "smart" LiFEPO charger? Such a charger would not know if an individual cell goes out of balance and hits 3.65V well before the other ones. If this is the case (which is not unlikely), then the BMS would have to step in every single time. Even if I can adjust the total charge voltage down, nothing would guarantee that a single cell would not hit 3.65V before the whole pack reaches the charge voltage. Obviously that's what the BMS is for. Therefore, I think of "overvoltage protection" as a needed routine feature, rather than as "uh oh, something went wrong". Again, I'm just thinking out loud here; there is obviously a lot that I don't know about this topic.

These are all good points. Have you been able to find out what the charge and float voltage is for the Delta charger? If you let your battery charge up for ~12 hours, at what voltage do the cells top out?

 

[rio]

These are all good points. Have you been able to find out what the charge and float voltage is for the Delta charger? If you let your battery charge up for ~12 hours, at what voltage do the cells top out?

I have not. It might be a good idea to reach out to them about this. @AMDPower, do you have a contact point for them? I recall you had some communication with them in the past.

 

[Prefersdirt]

My wife has given me grief re: the pricing here, but she'd rather not pay $800 every 2 years for environmentally unfriendly lead boxes either.

Realize these batteries can also be used to run an inverter when the power is out. All you would need to buy is a 48V inverter. Imagine your neighbors faces when the power is out and you go get the lawn mower!

 

[Hedges]

In that case buy yourself an inverter/charger, one with a decent Lithium profile.

Me? I would use Sunny Island and REC BMS, but that might cost more than your lawnmower
There is probably a reasonably budget-friendly one. MPP?

To make it easy and safe, drive the mower over to your breaker panel and plug inverter output into an interlocked generator input.
There isn't a great way to do it from your remote shed. One guy thought he could switch inverter input & output onto the AC feed back to house and main panel, but that's like a suicide cord and no disconnect from grid.

 

[Buff]

Realize these batteries can also be used to run an inverter when the power is out. All you would need to buy is a 48V inverter. Imagine your neighbors faces when the power is out and you go get the lawn mower!

This is exactly what I do with mine. I just have a small 1500 watt Aims one but it is enough to power the fridge and some lights. We don't have many outages where I live so I didn't want to spend a ton of money.

 

[kensiko]

Hello all, I have a Ryobi Zero Turn 100 Ah and I know the lead-acid batteries won't last much and looking on what I'll use next. I really want Lithium but I'd rather have a smaller one that I can bring inside for the winter.

I'm getting a Sur-ron with a 60V battery 32 Ah so I could possibly use it. I'm curious if the controller will accept 60V as it's already OK with 52V with the current lead-acid batteries or I really need a DC-DC converter with at least 3000 Watts.

 

[Ampster]

I'm curious if the controller will accept 60V as it's already OK with 52V with the current lead-acid batteries or I really need a DC-DC converter with at least 3000 Watts.

60 volts or so seems to be an inflection point for some electronic components before the next level. There is really no way to know without knowing the specs of the components. Perhaps Ryobi might know. My inverter manufacturer is real clear that 64 volts is the absolute battery maximum. Is the battery you are buying 60 volts nominal? At a full charge could it be even more?

 

[kensiko]

60 volts or so seems to be an inflection point for some electronic components before the next level. There is really no way to know without knowing the specs of the components. Perhaps Ryobi might know. My inverter manufacturer is real clear that 64 volts is the absolute battery maximum. Is the battery you are buying 60 volts nominal? At a full charge could it be even more?

Yes that's something I need to check, I'll have the bike next Saturday

 

[Hedges]

How about connecting a (smaller) DC/DC converter from your 60V lithium to the tired AGM?
I think the AGM will still deliver surge for hills, just have diminished capacity.
So add a spare "tank" to keep it topped off.

 

[kensiko]

That to would be great, I would need to find a place to attach the li-ion battery

 

[Hedges]

One more out-of-the-box idea is get an inverter that can take your lithium battery. MPP maybe? But you want small, and won't use it for charging lithium.
Carry battery and inverter to feed charger while mowing. Calculate charge time/rate to see if that makes any sense, would help during mowing time.
You'll have it as a portable power station for use elsewhere.

 

[kensiko]

Ok I got the bike, I measured 63V at 70% and the charger has a cutoff at 67V (printed on it), it's on the high side.

But I have to confess my stupidity, I made a mistake, I'll have to clap myself for a while for plugging the positive cable into the 10 amp meter plug on my multimeter. It was quite a flash and the connector on the battery melted for 1/8 on one side. I cleaned everything and removed some leftover copper and tried it on the bike, the connection is still good it's not getting hot, but I guess I'll have to replace the connector on the battery in the future.