Removal of AGM battery & installation of lithium battery
First, you have to remove the covers of the seat frame. To do this, loosen four screws on the left and right. The two parts at the front and back are just clipped in.
Then it’s on to the seat itself. You can take it out together with the rotating console. To do this, three screws must be loosened at the top of each side, which can be accessed by turning the seat. It would help if you used sensible bit attachments. Otherwise, the screws installed here tend to turn around. That’s why we had to drill out a screw last time.
If you have loosened the 6 visible screws and are wondering why the seat still cannot be removed, look again from below on each side because two more nuts need to be loosened. Then disconnect the airbag sensor cable and take the seat out. Attention: the seat is heavy, and ensure the airbag sensor cable is not caught anywhere. In addition, from now on, you should no longer turn the ignition key. Otherwise, an error message may appear on the onboard computer.
The batteries are now exposed. You should switch off the entire onboard electronics and disconnect the PWM controller and starter battery fuses before tampering with them.
Our batteries were still secured against slipping with a perforated metal strap. When that was solved, all cables and components were exposed.
If you’re wondering why we have so many cables: on the one hand, that’s because we connected two batteries in parallel. I.e. the two plus and minus poles of the two batteries are connected, and on the other hand, because we have installed a second solar charge controller for our mobile solar bag at the back here.
Now comes the point representing an internal hurdle for many: getting to the battery poles. And healthy caution is the right thing to do, but if you pay attention to the simplest things, you can’t do too much wrong. On the one hand, it is important that you always first disconnect the cable from the negative pole and only then the cable from the positive pole (when installing, the other way around: first connect the plus and then the minus) and, on the other hand, that the poles are not mixed up: i.e. only positive cables belong to the positive pole and ground cables only belong to the negative pole.
Dirk is always doubly careful and covers all open cable ends with a piece of heat-shrink tubing so that there is no contact or short circuit anywhere.
And when all the cables were loosened and secured, we could remove the two batteries. At just under 30kg each, it’s quite a feat of strength. Then it was the perfect moment to vacuum through and put back that piece of floor insulation that we had to cut out back in Malaysia when we installed those two AGM batteries, as the batteries were a bit too tall to fit under the seat otherwise.
Everything was prepared to insert the new RV battery. Since it is quite a bit smaller than our previous batteries, Dirk has secured it with another tension belt and two wooden strips so that it cannot slide back and forth or from left to right.
And since there was no additional space on the side, we also packed the solar charge controller for our solar bag on the side. There would be room for an inverter if we ever want to install one.
After the battery was secured, it was time to connect it. The Lutron underseat batteries have M8 pole screws – so we could plug our existing cables with M8 ring lugs onto them as I said: first plus and then minus. Then we connected the temperature sensors of our two chargers to the negative pole.
Then put the cap back on to protect the poles, and you’re done. At least almost, because, of course, you want your driver’s seat back. It is reinserted and screwed in place. Finally, the facings are back to the seat frame, and the conversion is done.
Charging technology for lithium batteries
We have heard and repeatedly read that you must replace your entire charging technology in the camper if you want to install a lithium battery. On the other hand, manufacturers of lithium batteries advertise that you can continue to use your old chargers.
We wanted to get to the bottom of this topic and did extensive research. We looked at different manufacturers, and it’s always the same: no, smart lithium batteries with their battery management system (BMS) can handle different charging characteristics and voltages.
At Renogy, for example, it says quite specifically (and I’m now quoting from the website): “Modern LiFePo4 batteries like the Renogy can be charged with any 12V lead charger with an end-of-charge voltage between 14.2V and 14.6V. Even an old 13.8V charger from the first generation of 12V gel batteries can charge a lithium battery. For example, it is only fully charged up to 90%, but this does not damage the battery.”
That sounds like you shouldn’t have to worry about it. But that’s not entirely true. Because if you look closely, there are three main limitations:
A charging voltage that is too low is okay, but charging voltages that are too high (i.e. everything above 14.6 V) should be avoided. Although charging voltages that are too high do not damage the battery, since the internal BMS would automatically prevent charging in such cases, the battery cannot be charged then.
No chargers with a desulfation program. Some chargers have a special charging program that can partially restore deeply discharged batteries. For this purpose, a very high voltage is charged for this purpose to overcome the higher charging resistance caused by the sulphation. So here, too, too high charging voltages would occur, which lithium iron phosphate batteries cannot tolerate (and at which good BMS switch off accordingly).
A charging booster is required for fast charging in modern vehicles since the alternator switches off early here, and a device is therefore required that fools the alternator into thinking that electricity is still needed. This known problem affects all battery types and is why almost all RV builders have been installing charging boosters in their vehicles since 2018. With lithium batteries, however, a charging booster/charger converter is particularly advisable since this is the only way to achieve the high charging currents, which are a great advantage of LiFePO4 batteries (and the batteries can only be recharged particularly quickly in this way).
These are all things that are not rocket science. Above all, you must ensure you don’t choose a charging program that works with too high a voltage.
With our battery, the maximum (and at the same time optimal) end-of-charge voltage is specified as 14.4-14.6 V. If I can’t set a LiFePO4 battery program on my chargers now, I’ll use one that is as close as possible – as long as it’s not over it.
With our solar charge controller, for example, I could select AGM 1, and the battery would be fine; AGM 2, on the other hand, would have too high a voltage.
However, we already have a LiFePO4 setting option on our two solar charge controllers and the charge booster. And above all, the two Votronic devices are now a few years old, so I assume that most devices now have special charging programs for lithium batteries anyway.