How to choose the most suitable battery type | Flooded AGM or Lithium | for your offgrid power project

Should you use a flooded Lead Acid, AGM, Gel, or Lithium battery?

Selecting the right battery technology for your power project whether it is an off-grid cabin, RV or residential backup power solution is key to realizing a  successful power project – one that matches your expectations is reliable and fits within your budget.

Guiding questions to help you decide on the most suitable battery type for you

Here are some questions from experience that you may find useful in informing your choice of battery type:

  • How much are you willing to spend on your battery bank?
  • Do you have sufficient or limited space for your battery installation?
  • When your battery is installed, are you likely to have spillages if the battery pack is not upright, there are shocks or vibrations?
  • Is it critical for your application that your battery lasts as long as possible or are you okay with replacing your battery every 3-4 years?

Selection criteria for Flooded AGM Gel or Lithium battery types

These simple criteria can help you choose the most suitable battery type for your project.

Choose Lithium battery types if:

  • You need to keep the weight of your battery bank to a minimum for example – if you carry your power project around  in a  backpack or a portable solar generator for your camping trips. Lithium batteries can be as weigh for as low as 50% of the weight of a Lead Acid battery of the same capacity.
  • You have limited installation space.  Lithium batteries store more power  per unit volume (energy density) compared to AGM, Gel or Flooded batteries which take up almost the same volume.
  • You are looking for a maintenance free battery – no topping up of the battery solution
  • There is risk of spills from your battery from shocks, vibrations or other sudden movements  of the battery for example in a scooter, wheelchair, rechargeable lamp
  • Want a battery with the longest lifespan with good battery management.

Here is an indicative guide of no. of cycles (a measure of the expected lifespan of a battery) for the different battery types (from

Deep cycle AGM 600 cycles at 50% DOD
Deep cycle Gel 750 cycles at 50% DOD
Deep cycle Lithium 7000 cycles at 80% DOD

And you have the budgetLithium batteries are the most expensive batteries of the lot followed by Gel, AGM and Flooded batteries.

Choose Gel batteries if:

  • You are looking for a maintenance battery
  • There is a high risk of spills of electrolyte – from shocks or vibrations
  • You need a battery with a decent lifespan – GEL batteries can last for 7+ years with good management practices.
  • Do not plan to use it for engine starts

And you have budget. GEL batteries tend to be slightly more expensive than AGM but cheaper than Lithium batteries.

Choose AGM batteries if:

  • You are looking for a maintenance battery
  • You need a leak and spill-proof battery
  • Are looking for flexibility in installation of your batteries because of space. For example, you may need to install the battery on the side.
  • You are okay with replacing your battery bank approximately every 2-5 years depending on quality of manufacture and good battery management practices.

And you have a limited budget. AGM batteries are generally cheaper than both Gel and Lithium batteries.

Consider Flooded Lead Acid batteries if:

  • The battery will be mounted in a fixed vertical position – to minimize spills
  • There is proper ventilation – these batteries can give off hydrogen during charging

And have a low budget. Flooded lead-acid batteries are the least expensive of the lot.

Common applications for | Flooded AGM Gel Lithium battery technologies

AGM and Gel battery types are commonly found in solar panel and power backup systems electric vehicles provided the use is not for engine starting for Gel, scooters,  wheelchairs.

Lithium batteries can also be found in residential solar applications, backup power systems in caravans, boat systems, and others where it is important to have lightweight battery packs.

Flooded Lead-acid batteries are now less common and are used in residential solar and backup power applications.

Related questions

# 1. What is the difference between AGM (absorbent glass mat) vs lead acid batteries?

Both battery types contain Lead-acid. AGM batteries are made of Lead-acid enclosed in an absorbent glass mat hence the spill-proof properties. They are sealed and it is not possible for one to access, top up or monitor the electrolyte level.

Flooded Lead-acid battery types allow the user to access, top up or monitor the electrolyte level and top -up with distilled water should the water level below.

AGM batteries though slightly more expensive than Flooded battery types are more convenient to use, easy to maintain unlike Flooded batteries that:

  • require maintenance
  • can spill and leak electrolyte
  • have higher self-discharge rate compared to AGM batteries when stored for a long time.
  • No flexibility in installation options -Flooded Lead Acid batteries need to be installed vertically.

# 2. What are differences and advantages of AGM vs Lithium battery types?

Lithium batteries are more expensive than AGM battery types. At the time of writing this post, a Lithium battery costs about 3 times the price of an AGM battery of the same capacity.

Lithium batteries have more usable capacity i.e. can be discharged to 90% of their capacity compared to  50% for AGM batteries

Lithium batteries weigh much less than AGM or Gel battery types and have a longer lifespan compared to AGM batteries

# 3. What are differences and advantages of Flooded vs Lithium battery types?

Flooded Lead Acid batteries are cheaper than Lithium batteries. Flooded Lead Acid batteries however have a less usable capacity of 30- 50% compared to 90% for Lithium battery types, are heavier, and do not last as long as the lithium battery types.

# 4. What is the difference between maintenance free  and  non maintenance free batteries?

Maintenance-free batteries types are sealed and do not require the user to periodically top-up with distilled water when the level is low to maintain good performance, unlike non maintenance free batteries.

Examples of Maintenance-free batteries are AGM, Gel, and Lithium battery types while non-maintenance free include the flooded battery types.

In summary, if your goal is to have a long battery service life and budget is not an issue, then definitely consider Lithium type batteries. They are light-weight, do not release hydrogen, and typically can be discharged up to 90% of their capacity without damage.

Gel battery types have a long shelf life when used in float applications, can resist shocks and vibrations are maintenance-free but are not suitable for high discharge applications like engine starts. They tend to be more expensive compared to AGM and Flooded batteries.

If you are okay with 3-4 years of service life, need a maintenance-free battery that can handle shocks and vibrations then consider AGM.

AGM batteries are budget-friendly and can handle high discharge applications reasonably well though should be discharged to 50% for best service life.

Flooded Lead-acid batteries are more affordable compared to all the other battery types but need periodic maintenance, need to be installed upright to avoid spills, and can discharge explosive hydrogen during the charging process.

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