SERIES-CONNECTED LITHIUM BATTERIES
Series connection of 12-volt lithium batteries is a solution where a 24, 36 or 48-volt battery bank is needed.
Here we inform about our experiences with Makspower lithium batteries
What to be aware of when series-connecting lithium batteries
Published Friday 24.11.2023 - Written by: Johan Fr. Bruenech
Some lithium batteries cannot be connected in series. All Makspower Lithium batteries can be connected in series
The reason is usually that the BMS, Battery Management System, electronics are not designed for series connection. As a rule, this is because the BMS is poorly dimensioned to make the battery as cheap as possible. Makspower lithium batteries have always been supplied with a solid BMS that is designed for series connection up to 48 volts.
Makspower has delivered a number of 24 volt solutions for large boats such as:
Boat
Eileen II, 82 foot sailboat
Grace, 120 foot motorboat
Ender Pearl, 76 foot sailboat
My CoCo, 67 foot motorboat
Centaurus, 70 foot motorboat
Battery bank
(600 Ah in 24 volts)
(900 Ah in 24 volts)
(900 Ah in 24 volts)
(900 Ah in 24 volts)
(600 Ah in 24 volts)
These boats are very power hungry and the batteries are run hard.
Examples of 24 volt installations
Centaurus (70 ft powerboat) 600 Ah lithium battery bank in 24 volt
The boat has been upgraded with Makspower 12-volt lithium batteries connected in series to 600 Ah in 24 volts. The Makspower batteries have been in operation for six years and show no signs of weakening. In Centaurus, it was necessary to replace the AGM batteries every year. The AGM batteries no longer lasted. It was expensive and a lot of hassle to change the batteries once a year.
EnderPearl (CNB 76 ft) sailboat, 900 Ah lithium battery bank in 24 volt
A large sailboat that is actively sailed in regattas with a very large crew. The battery bank has been in heavy use for five years and shows no signs of weakness.
Important when connecting 12 volt lithium batteries in series to 24 volts or more
For each battery to have the same starting point, they must be charged before they are connected in series. When they start equally, they will reach the top and bottom at the same time. This means that no batteries are left behind. A battery that is not working in sync with the other batteries will affect the entire battery bank, which in turn can become unbalanced. As a result, the bank loses much of its capacity and the charging source may struggle to charge correctly.
Lithium batteries and battery balancers
There are battery balancers that equalize any voltage differences between the batteries. Makspower has not needed to use battery balancers in any of our installations. If voltage differences are detected in the battery bank, we recommend checking whether power is being drawn from individual batteries, checking for poor cable connections or anything else that may cause some batteries to not keep up when charging or using power. A battery balancer will not "repair" a fault or weakness in the battery bank.
Some tips for choosing lithium batteries
Expand the battery bank later
Think about what you're going to use the battery bank for now and possibly in the future. A Makspower battery bank can be expanded later, unlike lead-acid batteries, which should preferably come from the same pallet.
How much power should I be able to draw from the battery bank now and later?
The number of batteries, the number of BMSs and how powerful the BMS is will affect how much power can be drawn from the battery bank and recharged.
An inverter can draw a lot of power
Charging the batteries with a lot of power is usually not the bottleneck. If you install an inverter to heat hot water, use hair dryers, household equipment and other things that give us that good holiday feeling, the bank must be dimensioned correctly.
A large bank with a powerful BMS can handle the tasks of today and tomorrow.
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