diy solar

diy solar

Going Lithium

Factsmanmp

New Member
Joined
Mar 3, 2023
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44
Location
Riverside CA
Ok, updating my 2005 class c motor home with solar and lithium. Doing it in phases. Started with (2) Coleman 100 wt panels and a Renogy 40 A charge controller. Now I want to swap my (2) 6 volt Trojan with a SOK 206 ah heated battery as it will fit in the compartment under the step. Can I wait to add the Renogy DC to DC charger and change the existing WFCO AD power Converter?
 
Please provide the model and link the manual for your existing converter. MOST converters can work fine with Lithium UNLESS you plan to recharge primarily with a generator.
 
Existing us a WF 8845. I called WFCO and was told the existing would charge a lithium battery but only up to 80% so they recommended I change to a WF 9845-AD. I do have an onboard 4kw generator but wanted to limit its usage.
 
Can you link the manual? I can't find one.

WFCO is motivated to sell you a new converter. I'm motivated to educate you to make the best decision for your use case.

Issue with all RV converters is typically the minimally sized wire between the batteries and the converter typically far apart that results in an excessive voltage drop. This worsens the issue with Lithium charging because the converter "sees" a higher voltage due to wire resistance and drops to a lower absorption voltage typically after 15-30 minutes. This means that a LFP battery may be charged at a lower current as a result. If your wire run is short, this is not a major concern.

The charging is still at least as fast as lead-acid, but it's not as good as it can be, and even with dedicated Lithium converters , it is still not optimal.

Preferred charge voltage: 14.4-14.6V
Acceptable charge voltage: 13.8V
Float voltage: 13.5V optimal, 13.2-13.6V acceptable.

If your converter performs as above (14.4 bulk, 13.8V absorption and 13.2V float is a common schedule), you will absolutely, positively get the battery to > 95% SoC on SHORE power over several hours.

On generator, it depends how bad the voltage drop is. If it's typical, your charge to 80% will be pretty quick - faster than lead. If you pay attention and shut down the generator as the current tapers significantly, you'll maximize your efficiency. If you let it run and fall to absorption, you will charge like lead acid from that point on.

In most cases, your best solution is to install a charger or second converter AT the battery location to minimize voltage drop. A Powermax PM3 can be set to the desired bulk voltage, is pretty cheap and installs quickly.

If you can verify sane voltages, I would encourage you to try out your existing converter before making any decision.
 
Quick mode sounds awesome and better than most I've seen. 4h @ 14.4V should get you to darn near full at near max amps unless your wiring is really poor. The vast majority of charging occurs at or below 13.8V measured at the battery terminals.

DEFINITELY try it before you move on.
 
Quick mode sounds awesome and better than most I've seen. 4h @ 14.4V should get you to darn near full at near max amps unless your wiring is really poor. The vast majority of charging occurs at or below 13.8V measured at the battery terminals.

DEFINITELY try it before you move on.
Yeah and the unit is only 3 ft from batteries.
I’ll check wire size too. Thank you so much for your input.
 
Yeah and the unit is only 3 ft from batteries.
I’ll check wire size too. Thank you so much for your input.

6awg or better should cut it for such a short run.


Just make sure your connections/crimps, etc. are of high quality, and you properly torque the connections.

45A for 4h = 180Ah, so unless you've completely depleted your battery, it will be hard to not get 90% charged in those 4 hours, and if charging for less than 4 hours, you should get close enough to 100% to not matter.

BTW... if not already in the plan, recommend a good battery monitor UNLESS the battery smart BMS accurately reports SoC. BMS SoC is generally accurate enough after it's been fully charged.
 
6awg or better should cut it for such a short run.


Just make sure your connections/crimps, etc. are of high quality, and you properly torque the connections.

45A for 4h = 180Ah, so unless you've completely depleted your battery, it will be hard to not get 90% charged in those 4 hours, and if charging for less than 4 hours, you should get close enough to 100% to not matter.

BTW... if not already in the plan, recommend a good battery monitor UNLESS the battery smart BMS accurately reports SoC. BMS SoC is generally accurate enough after it's been fully charged.
Well, time flies when life gets busy. Here I am…… 6 months later….. but back on the solar trail. Just installed a Dc to Dc charger and changed Emergency Start switch to a ignition power switch with a nice red light to remind me when alternator is charging the house batteries. Speaking of house batteries, now I can swap out the 2 Trojan 6 volt batteries for a SOK 206 ah heated with blue tooth….. and have no fear of frying my alternator.
The previously mentioned WFCO converter decided on its own to give up and retire so I will be replacing it with a “lithium approved” converter and keeping it in the same location… about 3 feet from my battery. I’m thinking about getting an inverter also and it will be installed about 3 ft from the battery on the other side. Should I go ahead with a 3000 w inverter thinking I might add a second SOK 206 ah battery in the future?
 
If you can return it, I would recommend returning the Renogy charge controller. Even after getting the Bluetooth dongle and changing all the USER settings, my Renogy Rover 30A MPPT is still sending up to 16.5V to the lithium battery. Not long enough to trigger the protection of the battery’s BMS, but any amount of time is too long IMO. I tried rectifying this with renogy tech support to no avail. They’re nice and seem willing to help, but communication with them is maddening, like the “who’s on first?” skit.

Go Victron for a few dollars more.
 
If you can return it, I would recommend returning the Renogy charge controller. Even after getting the Bluetooth dongle and changing all the USER settings, my Renogy Rover 30A MPPT is still sending up to 16.5V to the lithium battery. Not long enough to trigger the protection of the battery’s BMS, but any amount of time is too long IMO. I tried rectifying this with renogy tech support to no avail. They’re nice and seem willing to help, but communication with them is maddening, like the “who’s on first?” skit.

Go Victron for a few dollars more.
Thanks for the response. So far the River 40A controller has been ok with the existing lead acid batteries. I’ll keep an eye on it when I switch to lithium batteries. I’ve had it over a year so probably can’t send it back
 
Thanks for the response. So far the River 40A controller has been ok with the existing lead acid batteries. I’ll keep an eye on it when I switch to lithium batteries. I’ve had it over a year so probably can’t send it back

Thing is you can’t know that you can’t see nor change all the settings without the Bluetooth dongle. High voltage disconnect is the setting you want to change. In USER mode, its default is set to 17v. You need the dongle to change it. This controller nearly ruined my brand new battery.
 
If you can return it, I would recommend returning the Renogy charge controller. Even after getting the Bluetooth dongle and changing all the USER settings, my Renogy Rover 30A MPPT is still sending up to 16.5V to the lithium battery. Not long enough to trigger the protection of the battery’s BMS, but any amount of time is too long IMO. I tried rectifying this with renogy tech support to no avail. They’re nice and seem willing to help, but communication with them is maddening, like the “who’s on first?” skit.

Go Victron for a few dollars more.

I've seen Victron MPPT hit 12V LFP batteries with 20V and more due to BMS charge cut off. Are you sure that's not what's happening?

Thing is you can’t know that you can’t see nor change all the settings without the Bluetooth dongle. High voltage disconnect is the setting you want to change. In USER mode, its default is set to 17v. You need the dongle to change it. This controller nearly ruined my brand new battery.

Does that setting apply to the MPPT in general or is it load port specific?
 
I've seen Victron MPPT hit 12V LFP batteries with 20V and more due to BMS charge cut off. Are you sure that's not what's happening?

Good question. I’m not sure. Can you explain more about why or how this might happen?

Also, the BMS is what is ending the charge. Charge MOSFET is off when this happens. Doesn’t seem to be the Renogy controller that ends charging. Just installed the Victron so we’ll see if it’s different. Battery is Powerurus 12v 200Ah.

Does that setting apply to the MPPT in general or is it load port specific?

It’s not load port specific, as I have the load port turned off.

I’m not entirely sure that the Rover is actually overcharging the battery but it does seem that way.

One day the BMS wigged out. Voltage was spinning all over, from 12.8v to 14.0v. Without any loads. Disconnecting the battery from the system for 20 minutes seemed to have reset something. This wig out session coincided with the Rover history showing 16-17v battery voltage, shown on the Renogy’s app in the history section.
 
If your converter performs as above (14.4 bulk, 13.8V absorption and 13.2V float is a common schedule), you will absolutely, positively get the battery to > 95% SoC on SHORE power over several hours.

On generator, it depends how bad the voltage drop is. If it's typical, your charge to 80% will be pretty quick - faster than lead. If you pay attention and shut down the generator as the current tapers significantly, you'll maximize your efficiency. If you let it run and fall to absorption, you will charge like lead acid from that point on.
Can you help me understand the key difference between shore and generator in this case? I'm assuming that the converter does not know the difference where its power comes from. So I'm assuming that you mentioned this simply because it's wasteful to run a generator just to get the last few sips in absorption? Thanks (sorry to intrude)
 
Good question. I’m not sure. Can you explain more about why or how this might happen?

One or more cells is over the voltage limit.

Also, the BMS is what is ending the charge. Charge MOSFET is off when this happens.

Okay, so you have a battery problem, not a Renogy problem.

Doesn’t seem to be the Renogy controller that ends charging.

Sound like it's because the battery is out of balance, and the BMS protection triggers before the Renogy charge criteria are met.

Have you tried setting boost to 13.8V?

Just installed the Victron so we’ll see if it’s different. Battery is Powerurus 12v 200Ah.

I'm no fan of Renogy, and you know how I feel about Victron, but it really sounds like you have a battery problem. This is extremely common and pretty much all "canned" batteries - including EG4, SOK, Trophy, etc., will trigger BMS protection due to cell imbalance when initially put in service.

In other words, I expect you'll have the same issue with Victron.

This comes from the fact that the battery is disconnected from the charge circuit, and the charger can't clamp down on it's output fast enough to not cause at least a small voltage spike.

It’s not load port specific, as I have the load port turned off.

Just because it's turned off doesn't mean that option won't be displayed. I'm 99.9% certain it's purely for load port cut off. There's no reason for the charger to ever go over its boost voltage in normal operation, so why is there even a disconnect voltage? It's there to protect the device on the load port. If some other device on the DC bus pushes battery voltage over the cut-off, then the load port circuit will open and protect the devices on the load port from over-voltage.

I’m not entirely sure that the Rover is actually overcharging the battery but it does seem that way.

It doesn't sound like it.

One day the BMS wigged out. Voltage was spinning all over, from 12.8v to 14.0v. Without any loads. Disconnecting the battery from the system for 20 minutes seemed to have reset something. This wig out session coincided with the Rover history showing 16-17v battery voltage, shown on the Renogy’s app in the history section.

This sounds exclusively like an issue with the battery BMS cutting off charge and the Renogy spiking because the "load" of the battery was removed from the charger.

Set boost to 13.8V and see if the issue goes away.
 
Can you help me understand the key difference between shore and generator in this case? I'm assuming that the converter does not know the difference where its power comes from. So I'm assuming that you mentioned this simply because it's wasteful to run a generator just to get the last few sips in absorption? Thanks (sorry to intrude)

Yep. This is less true with LFP than with lead-acid. Lead-acid absorption typically takes 2+ hours vs. 15-30 minutes for LFP AT higher votlages.

The "absorption" at 13.6V for LFP will only supply a limited current to the battery, and as the battery approaches full, it's going to diminish even more. An extended charge (overnight?) will be needed to get to a high state of charge. 8 hours on shore is far less costly than 8 hours on a generator to top it off.
 
One or more cells is over the voltage limit.



Okay, so you have a battery problem, not a Renogy problem.



Sound like it's because the battery is out of balance, and the BMS protection triggers before the Renogy charge criteria are met.

Have you tried setting boost to 13.8V?



I'm no fan of Renogy, and you know how I feel about Victron, but it really sounds like you have a battery problem. This is extremely common and pretty much all "canned" batteries - including EG4, SOK, Trophy, etc., will trigger BMS protection due to cell imbalance when initially put in service.

In other words, I expect you'll have the same issue with Victron.

This comes from the fact that the battery is disconnected from the charge circuit, and the charger can't clamp down on it's output fast enough to not cause at least a small voltage spike.



Just because it's turned off doesn't mean that option won't be displayed. I'm 99.9% certain it's purely for load port cut off. There's no reason for the charger to ever go over its boost voltage in normal operation, so why is there even a disconnect voltage? It's there to protect the device on the load port. If some other device on the DC bus pushes battery voltage over the cut-off, then the load port circuit will open and protect the devices on the load port from over-voltage.



It doesn't sound like it.



This sounds exclusively like an issue with the battery BMS cutting off charge and the Renogy spiking because the "load" of the battery was removed from the charger.

Set boost to 13.8V and see if the issue goes away.

Thanks so much for this! I’ll give the 13.8v bulk charge a try.
 
Have you tried setting boost to 13.8V?

So I have bulk set to 13.8v on both the Victron 100/30 and IP22 12/30. Should I set the absorb time for as long as possible? Currently set for 9h on the charge controller and 12h on the ac charger. Would it be helpful to set it for more than 24-48 hours?
 
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