- Written by Aaron King
- Category: Building Tips
- Published: 30 May 2013
- Hits: 372
LaGrange L1 electric skateboards are designed to be powered by hobby-grade electronics. These systems can handle a variety of battery types and input voltages depending on the components that are used. This article describes some of the options and considerations regarding the batteries used to power your electric skateboard.
(Note: Hyperlinks are supplied as references and are not affiliated with the author or RRBS.)
Battery Placement: Backpack battery vs. on-board battery
Battery packs are by far the heaviest components in electric vehicles. At RedRock Boardshop, we promote the use of a remote battery setup, where the battery pack is carried in a backpack and connected to the board by an electrical cable or “leash”. By eliminating the battery from the skateboard deck, LaGrange powered boards weigh only a few pounds more than a traditional skateboard. This preserves the board’s handling and ride quality - Riders can effortlessly carve up and down hills on a board that feels agile and familiar. The backpack battery is also simple to set up and is ideal for commuting as it allows you to carry tools, cargo, and additional battery packs for extend range. The downside of the backpack battery is that the leash can be awkward at times and it will frequently get unplugged by novice riders.
Simple Image Gallery Extended
Alternatively, battery packs can be mounted directly to your skateboard rather than carried in a backpack. This usually involves screwing brackets or a protective case onto the deck of your board to hold the battery packs. The on-board battery setup is considered an advanced build because it currently requires additional parts and custom assembly.
The on-board battery makes your electric skateboard more convenient to ride and is an ideal setup for frequent short trips. Because the batteries will add substantial weight to the board (which negatively affects its handling and feel), I only recommend using small LiPo batteries in an on-board setup. Also, if you have an on-board battery, you can always add a backpack battery setup to increase your range for longer rides – the best of both worlds. One of my current boards uses a 2.86Ah on-board LiPo battery for short rides and a 13Ah NiMH backpack battery for longer excursions. A simple battery bracket can be made can be made similarly to RRBS’s top-mount E-Bracket (see photo).
Battery Chemistry: SLA, NiMH, and LiPo
This section describes some of the common types of batteries used to power LaGrange L1 electric skateboards: sealed lead-acid (SLA), nickel–metal hydride (NiMH), and lithium polymer (LiPo).
SLA batteries are the type used in electric golf carts and in motorcycles to start their engines. They are a great beginner battery because they are inexpensive, easy to use, and low maintenance. However, SLA batteries are large and heavy compared to other battery chemistries. Although weight is less of an issue when using a backpack battery setup, 12Ah is the highest capacity of SLA battery packs that I recommend due to their high weight.
Individual SLA batteries typically come in 12-volts, and less often in 6-volts. RRBS recommends a 24v system if using SLA batteries. Ready-to-run 24v SLA battery systems are somewhat common from electric bike or scooter suppliers. Alternatively, an SLA battery pack can be built relatively easily by connecting four 6 volt batteries in series as seen in this photo of my homebuilt SLA pack (this 12Ah battery weighs 16.5-lbs and measures 1.75” x 11.75” x 7.75”). I had been using SLA battery packs for years before eventually switching to NiMH and LiPo packs.
NiMH battery packs are smaller in size and half the weight of similar SLA packs. NiMH packs require more maintenance than a SLA system - but when used properly, these batteries can have exceptionally long lives (1000s of charges). NiMH batteries are also environmentally friendly as they contain no toxic materials. They are cheaper than LiPO batteries but US prices seem to fluctuate a bit.
Individual NiMH batteries come as 1.2 volt cells (nominal). RRBS recommends an 18-20 cell (21.6-24v) battery system if using NiMH batteries. There aren’t a lot of choices available for high capacity NiMH Packs on the market. I have used this 10 Ah Flat pack for years with good results - even though the discharge rating on this battery seems very low. Some of the best battery packs that I have used have been hand made in our shop using 10Ah D-size cells and 13Ah F-size cells (See photos: 10Ah and 13Ah). Also, 20 cell (24v) packs are can be found in other small electric vehicles, so electric bike manufacturers may be a good source for complete ready-to-run battery systems. Alternatively, an 18-cell battery system could be made by connecting three common 6-cell battery packs in series.
For more information, check out this article on NiMH batteries.
LiPo batteries are the type found in modern high-end electronics like cellphones and laptops. They are also popular in the R/C industry and are therefore readily available at hobby shops. Lipo batteries are small, lightweight, and great for high performance applications but require more maintenance and have higher potential safety risks than other types of batteries. For these reasons, LiPo batteries are considered an advanced battery system.
Because these packs are popular in the R/C market, fully assembled packs are readily available at local and online hobby stores. Typically, the only assembly steps required for LiPo packs is soldering electrical connectors to the leads and adding some padding and/or armor to protect the packs from damage.
LiPo batteries carry 3.7 volts per cell (nominal). The number of cells in a LiPo pack is labeled as “s” – for example, a “6s” LiPo battery has 6 cells and 22.2 volts. RRBS recommends using a 6s battery pack for the typical LaGrange assembly. Alternatively, you could connect two 3s packs in series to make a 6s system.
All lithium batteries, including LiPos are at risk of exploding or catching fire if overcharged, overheated, short-circuited or damaged. RC enthusiasts take special precautions to ensure their battery leads are properly connected and insulated (and be careful while soldering!). There are several videos online that show LiPo batteries venting and catching fire after short-circuiting or being punctured – take notice of how much damage it takes (and how much time) before the packs become a safety concern. I was terrified by these batteries until I watched these videos. Although the possibility of explosion and fire is real, the risks of these batteries can be mitigated by careful use and by properly protecting the pack from potential harm.
LiPos are very sensitive and require specific care and maintenance. This involves balance charging, storage at a specific voltage, and not allowing the battery to get over-discharged. Most ESC’s have a programmable low-voltage cutoff (LVC) setting that prevents the battery from over-discharge. LiPo’s can be recharged several hundred to thousands of times if properly maintained. Charging, discharging, and storage all affect the lifespan – get it wrong and a LiPo is garbage in as little as one mistake.
For more information, check out this article on LiPo batteries... and this one too.
Battery current and capacity
The electronic systems of these skateboards can undergo high current draw during hard acceleration and hill climbing. Be sure to check the battery's discharge rating to ensure that it can supply high current (Amps) during peak discharge. From the data collected during my rides, the AVERAGE current is between 8-5 Amps and the PEAK discharge can be as high as 80 Amps (but only for a fraction of a second). I've got some reports on this data in case any nerds are interested. If you're pulling a lot of power, I recommend getting an in-line watt meter so you can keep track of your max amp draw.
The battery's discharge rating (see "C-value” for LiPo cells) indicates how many amps the battery can safely deliver while maintaining a proper voltage level. The effect of a higher rating shows up during acceleration where maximum amps are required. A pack with a higher rated discharge will out accelerate a lesser pack.
The capacity of the battery packs are measured in Amp-hours (Ah). A good estimate for range on a LaGrange powered electric skateboard is 1 mile of range for every 1 Ah of battery capacity.
You can also consider buying multiple smaller battery packs and connect them in series to increase the system’s voltage - or connect packs in parallel to increase the range (Ah) and discharge capacity (Amps) of your battery system.
Advice on Chargers and Charging
The type of charger you buy depends on the type of battery you intend to use (NiMH, SLA, or LiPo). Make sure the charger you select is compatible with the type of battery chemistry and the number of cells in your pack. Some advanced chargers let you switch settings to adjust for chemistry and cell count – which will allow you to upgrade your batteries in the future without having to get a new charger (see example). Also, many RC chargers are powered by 12-volts DC (for charging in the field) instead of 110-volts AC, so be sure to check the specifications or be prepared to also buy a 12-volt power source.
SLA battery charging:
24-volt SLA chargers are somewhat common from electric bike or scooter suppliers. Alternatively, common 12-volt car-battery chargers can charge individual 12v cells of a 24v system – be sure to use the low power setting.
These batteries must always be stored in a charged state. Leaving the battery in a discharged condition causes sulfation and may damage the battery.
NiMH battery charging:
24-volt NiMH chargers are available through several retailers (see example). NiMH batteries heat up when they become fully charged so they must be charged in open air - do not charge the batteries in your backpack! When the pack heats up, this indicates that the battery is fully charged and should be disconnected from the charger. Some chargers have temperature sensors to automatically stop the charging process when the cells heat up.
These batteries are relatively low maintenance but they benefit from occasional cycling (repeated full charging and discharging cycles). They also self-discharge by about 1% per day, so if you leave a NiMH battery sitting for a couple of months, it will need recharging before use.
LiPo battery charging:
LiPo batteries require more exact care than other battery chemistries. They can be easily damaged by improper charging or maintenance. LiPos are at risk of exploding or catching fire if overcharged, overheated, or damaged. Extra care must be taken when using with these batteries – double-check your charger’s settings and never leave your battery unsupervised while charging. There are also charger bags available to minimize any damage caused in the event of a catastrophic battery failure.
When charging LiPo batteries, each individual cell in the pack should be charged evenly. This is performed using the battery’s balancing leads and a LiPo balancing charger (see example). There are many balancing battery chargers available in the hobby market.
LiPo batteries should also be precisely discharged (to ~3.8-volts per cell) when they are to be stored for more than a day or so. Most LiPo chargers have a storage mode that will either charge or discharge your pack to the proper level.
I hope this helps in your decision on what type of battery to use with your board. To learn more in-depth information on batteries, be sure to check out Battery University.