Lithium Conversion Questions

[Gene Obie]

Since we have same coach you prompted me to add some pics. One shows the tap I made into one of the 2 wires going to "Ignition" connect back to "Genset" on Bird.

I previously had 6 lead acid. I was thinking of buying a new tray that I could configure better for the SOK I purchased since they needed to be turned sideways relative to original, but ended up having a local handyman here help with the job. He cut out the existing metal supports in the bottom of the tray and turned them sideways and then welded in pieces of old bed frame to "center"  the SOK in the tray. They are offset a bit from each other since we were afraid the screws bumps on the top of SOK might interfere (we did this before I had batteries in hand). It would have been tight if we hadn't done that but it probably would have fit. The tray was cleaned up, rust removed, bearings serviced and all painted. He only charge $80 for all his work so well worth it rather than replace the tray.. which would have required welding some mounts back on the new tray too so not just a simple drop in.

I had new short cables built at a shop just up the road to interconnect the SOKs but I'm still using original longer +/- cabling back to inverter. I put plywood under each battery with some rubber anti-vibration padding... the plan is to maybe build a "portable" insulation box around them if I get into some colder weather so that's part of the reason for the plywood. New SOK's have heaters I guess. I just use staps to hold each from bouncing out. One last thing I want to do is mold some plastic covers for the terminals with a bag of that InstaMorph moldable plastic I have sitting here, and to find a way to build a plastic cover over the shunt. Probably don't absolutely need it but feels better to help prevent a short.

I've also attached couple screenshots of the Thornwave Labs monitor phone app. The graphing could be better as I can't separately scale the plots (to view zoomed in current and voltage together for example)... but if you're good at excel you can export the log and play all you want. The cursors in the app are accurate though. This monitor has worked flawlessly for me.

No more banging my head and dealing with filling wet cells and acid!

Oh, and the extra blue wire you see goes back to chasis battery as Thornwave has a 2nd battery monitor input. And don't forget to pull the temperature sensor at the inverter to disable temp compensation.

[William Jordan]

Shouldn’t the shunt be on the negative , not the positive line? It is on my system.

[Gene Obie]

Thornwave monitor is designed to go on either. It's easier for me to have it up front to make connections and get access to it. Maybe not quite as safe with more exposed + terminals but I will cover it, and it's pretty well protected.

[Robert Lawrence]

I was reading your plan over and had another question.  Can you outline the modification you did to the BIRD unit to isolate the charging from the alternator.

[Gene Obie]

Robert, I've added to pic with descriptions. My Bird had the GENSET input disconnected. The GENSET input was designed to OPEN the Big Boy relay for systems with generators that couldn't charge both chassis and coach batteries at the same time. It's a 12V input same at BIRD IGNITION input. I'm assuming this GENSET input is also not used on your coach. Just splice one of the 2 IGNITION wires (doesn't matter which one) with another wire+terminal and attach to GENSET input. That is the only BIRD change.

Intellitec support confirmed the above mod seemed like simple solution to what I wanted to accomplish. He warned one issue may be that due to higher resting voltage of Lithium compared to my AGM that my lithium would charge AGM continuously when running on battery only. I tested this and did not find it to be the case. After a full charge, the resting Lithium voltage is a little higher than AGM and I found my Lithium charging my AGM at 1-2A... but after an hour or so both batteries banks were discharging. The lithiums discharge at a higher rate - but no cross charging after an hour. That 1-2A for an hour or 2 is really nothing and doesn't seem like it should be a problem. Seems any system with mixed batteries like this will have the same issue  unless you completely isolate the 2.

Another item to be aware of. When you turn ON the ignition switch on there is a 1-2second delay before Bird detects the condition and opens the Big Boy relay. I discovered this when reviewing my logs and noticed that one time when I quickly started the engine to move the coach a foot there was a large draw (360A) on the Lithium .. this was due to engine starter pulling current from the Lithium. This really shouldn't be a problem as long as BMS in Lithium doesn't trip. To avoid this I just turn ON ignition and pause 2 seconds before cranking.

As I've said before the logging capability of the Thornwave monitor allows me to literally pull logs from weeks back and review voltage, currents, power draw, temp, SOC, etc. I highly recommend it or something similar to be able to make sure everything is good with your setup.

[Bill Lampkin]

Nice work, Gene! I'm gonna have to measure my battery tray to see how much space is available. My FLA batteries won't last forever (I think I bought them in 2016). I saw the Thornwave unit a while back; how far can you roam from your batteries and still read the Thornwave data?
Again, nice work!

[Gene Obie]

Bill, I have no problems connecting to the Thornwave anywhere inside my coach. It's bluetooth so probably depends to some degree on how good the bluetooth is in your phone or tablet.